United States Patent (19)
`Yamazaki et al.
`
`|||||I|||||
`US00546O136A
`11) Patent Number:
`5,460,136
`45) Date of Patent:
`Oct. 24, 1995
`
`54 EVAPORATIVE FUEL-ADSORBING DEVICE
`AND EVAPORATIVE EMISSION CONTROL
`SYSTEM INCLUDING SAME
`
`75) Inventors: Kazumi Yamazaki, Kouichi Hidano;
`Teruo Wakashiro; Takeshi Hara, all
`of Wako; Tomoyuki Kawakami,
`Tochigi, all of Japan
`(73) Assignee: Honda Giken Kogyo Kabushiki
`Kaisha, Minato, Japan
`
`Appl. No.: 329,831
`(21
`Filed:
`Oct. 27, 1994
`(22
`Foreign Application Priority Data
`(30)
`Oct. 28, 1993 (JP)
`Japan ................................... 5-292782
`Dec. 27, 1993 - JP
`Japan .................................... 5-348572
`(51) Int. Cl. .......................... F02M 25/08
`(52) U.S. Cl. ............................................. 123/519; 123/520
`58) Field of Search ..................................... 123/516, 518,
`123/519, 520
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`... 123/519
`1/1982 Hiramatsu ...
`4,308,840
`... 123/59
`1/1990 Turner et al. ...
`4,894,072
`... 1231519
`4,919,103 4/1990 Ishiquro et al. .....
`... 123/519
`4,951,643 8/1990 Sato et al. ........
`... 123/519
`5,056,494 10/1991 Kayanuma ..
`5,111,795 5/1992 Thompson .............................. 123/519
`5,143,041
`9/1992 Franzke ................................... 1231516
`
`5,170,765 12/1992 Hoshino et al. ........................ 123/519
`FOREIGN PATENT DOCUMENTS
`1-159455 6/1989 Japan.
`Primary Examiner-Thomas N. Moulis
`Attorney, Agent, or Firm-Nikaido, Marmelstein, Murray &
`Oram
`
`ABSTRACT
`(57)
`An evaporative fuel-adsorbing device adsorbs evaporative
`fuel generated from a fuel tank of an internal combustion
`engine. A partition divides the interior of a casing at least
`into a first adsorbent chamber and a second adsorbent
`chamber. Adsorbents are charged in the first adsorbent
`chamber and the second adsorbent chamber, respectively,
`for adsorbing the evaporative fuel. The evaporative fuel
`from the fuel tank is permitted to flow into the first adsorbent
`chamber via a charging port provided therein. The evapo
`rative fuel desorbed from the adsorbents in the adsorbent
`chambers are permitted to flow out of the first adsorbent
`chamber via a purging port provided therein. The second
`adsorbent chamber is communicated with the atmosphere
`via an air-inlet port. The maximum flow rate of the evapo
`rative fuel through a communication passage connecting
`between the first and second adsorbent chambers is changed
`in dependence on at least one of an amount of the evapo
`rative fuel flowing into the evaporative fuel-adsorbing
`device and an amount of the evaporative fuel flowing out of
`same. An evaporative emission control system incorporating
`the evaporative fuel-adsorbing device is also provided.
`
`18 Claims, 6 Drawing Sheets
`
`
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`
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`
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`
`
`INTERNAL
`COMBUSTION
`ENGINE
`
`INGEVITY SOUTH CAROLINA, LLC, EXHIBIT 2004
`BASF Corporation v. Ingevity South Carolina, LLC
`IPR2019-00202
`
`

`

`U.S. Patent
`
`Oct. 24, 1995
`
`Sheet 1 of 6
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`5,460,136
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`INTERNAL
`COMBUSTION
`ENGINE
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`

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`U.S. Patent
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`Oct. 24, 1995
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`Sheet 2 of 6
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`5,460,136
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`FIG.2
`
`REON
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`
`
`REGION
`
`BYBASS PASSAGE
`CLOSED
`
`- - - -
`
`FLOW RATE
`
`

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`U.S. Patent
`
`Oct. 24, 1995
`
`Sheet 3 of 6
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`5,460,136
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`
`
`INTERNAL
`COMBUSTION
`ENGINE
`
`

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`U.S. Patent
`
`Oct. 24, 1995
`
`Sheet 4 of 6
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`5,460,136
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`FIG.4
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`10
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`444444444444
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`N N N
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`Y
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`U.S. Patent
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`Oct. 24, 1995
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`Sheet 5 of 6
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`5,460,136
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`FIG5
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`10
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`

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`U.S. Patent
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`Oct. 24, 1995
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`Sheet 6 of 6
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`5,460,136
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`FIG.6
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`27
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`SN
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`

`

`1.
`EWAPORATIVE FUEL-AOSORBNG DEVICE
`AND EVAPORATIVE EMISSION CONTROL
`SYSTEM.INCLUDING SAME
`
`5,460,136
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`2
`ting a simplified construction involving a purging passage
`connected thereto.
`It is a second object of the invention to provide an
`evaporative emission control system which is capable of
`enhancing the utilization factor of the adsorbent without
`increasing the amount of the adsorbent used, and at the same
`time has a simplified construction involving a purging
`passage connected to an evaporative fuel-adsorbing device
`thereof.
`To attain the first object, according to a first aspect of the
`invention, there is provided an evaporative fuel-adsorbing
`device for adsorbing an evaporative fuel generated from a
`fuel tank of an internal combustion engine, comprising:
`a casing;
`partition means arranged within the casing, the partition
`means dividing an interior of the casing at least into a
`first adsorbent chamber and a second adsorbent cham
`ber;
`absorbents charged, respectively, in the first adsorbent
`chamber and the second adsorbent chamber for adsorb
`ing the evaporative fuel;
`charging port means provided in the first adsorbent cham
`ber for permitting the evaporative fuel from the fuel
`tank to flow into the first adsorbent chamber,
`purging port means provided in the first adsorbent cham
`ber for permitting the evaporative fuel desorbed from
`the absorbents in the first and second adsorbent cham
`bers to flow out of the first adsorbent chamber;
`air-inlet port means provided in the second adsorbent
`chamber and communicating the second adsorbent
`chamber with the atmosphere;
`communication passage means connecting between the
`first adsorbent chamber and the second adsorbent
`chamber,
`flow rate-changing means for changing a maximum flow
`rate of the evaporative fuel through the communication
`passage means, in dependence on at least one of an
`amount of the evaporative fuel flowing into the evapo
`rative fuel-adsorbing device and an amount of the
`evaporative fuel flowing out of the evaporative fuel
`adsorbing device.
`Preferably, the charging port means is connected to the
`fuel tank, and the communication passage means comprises
`a first passage which is constantly open, and a second
`passage, the flow rate-changing means opening the second
`communication passage at least when the fuel tank is
`refueled.
`More preferably, the flow rate-changing means comprises
`valve means arranged in the second passage, the valve
`means opening at least when the fuel tank is refueled.
`Also preferably, the flow rate-changing means comprises
`valve means arranged in the second passage, the valve
`means opening when the fuel tank is refueled and when the
`evaporative fuel is purged from the evaporative fuel-adsorb
`ing device.
`Further preferably, the valve means arranged in the sec
`ond passage comprises a one-way valve which opens when
`pressure within the first adsorbent chamber is higher than
`pressure within the second adsorbent chamber by a prede
`termined amount or more.
`Still more preferably, the valve means arranged in the
`Second passage comprises a first one-way valve which opens
`when pressure within the first adsorbent chamber is higher
`than pressure within the second adsorbent chamber by a
`predetermined amount or more, and a second one-way valve
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to an evaporative fuel-adsorbing
`device for adsorbing evaporative fuel generated from a fuel
`tank of an internal combustion engine, and an evaporative
`emission control system for preventing evaporative fuel
`from being emitted into the atmosphere by the use of the
`evaporative fuel-adsorbing device.
`2. Prior Art
`Conventionally, an evaporative emission control system
`of this kind has been proposed by Japanese Provisional
`Patent Publication (Kokai) No. 1-159455. In addition to an
`ordinary canister for adsorbing evaporative fuel generated
`from a fuel tank when a vehicle in which the fuel tank is
`installed is parking or when an engine installed in the vehicle
`is operating, this evaporative emission control system
`includes a canister for exclusive use in refueling, which is
`adapted to adsorb evaporative fuel generated when the fuel
`tank is being refueled. Further, to solve the problem of a
`poor adsorbing efficiency of the ordinary canister due to a
`high flow velocity of evaporative fuel generated when the
`fuel tank is refueled, in the proposed evaporative emission
`control system, the canister for exclusive use in refueling is
`provided with partitions within the canister which divide its
`adsorbent-accommodating space into a plurality of layers,
`and the direction of flow of the evaporative fuel is changed
`to reduce the flow velocity of the evaporative fuel, thereby
`enhancing the adsorbing efficiency of the canister without
`increasing the size (ratio LID (length/diameter)) of the
`canister.
`However, with the conventional evaporative emission
`control system, the canister for refueling is intended exclu
`sively for refueling, and it is not used on occasions other
`than at refueling. Once the evaporative fuel adsorbed is
`purged into the engine, it becomes empty, i.e. contains no
`evaporative fuel, resulting in a lower utilization factor of the
`activated carbon. Further, two batches of activated carbon
`have to be provided as adsorbents, one for the canister for
`exclusive use in refueling, and the other for the ordinary
`canister, which results in use of an increased amount of
`activated carbon, leading to an increased cost. Further, it is
`required to provide a plurality of purging passages connect
`ing between the respective canisters and the intake passages
`for discharging evaporative fuel adsorbed in the canisters,
`which complicates the construction of the system.
`Further, in the conventional evaporative emission control
`system, in purging a large amount of evaporative fuel for
`enhancing the utilization factor of the adsorbent, the flow
`resistance of a communication passage connecting between
`one layer of the adsorbent and another layer divided by a
`partition is large since the communication passage is narrow,
`which prevents a sufficient amount of evaporative fuel from
`being purged. As a result, it takes much time to purge all the
`evaporative fuel adsorbed by the adsorbent, and hence if
`traveling of the vehicle is repeatedly carried out at short time
`intervals, evaporative fuel adsorbed in the canister for refu
`eling remains unpurged, resulting in a low utilization factor
`of the adsorbent.
`SUMMARY OF THE INVENTION
`It is a first object of the invention to provide an evapo
`rative fuel-adsorbing device which is capable of enhancing
`the utilization factor of the adsorbent without increasing the
`amount of the adsorbent used, and at the same time permit
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`3
`which opens when the pressure within the second adsorbent
`chamber is higher than the pressure within the first adsorbent
`chamber by a predetermined amount or more.
`Also preferably, the valve means arranged in the second
`passage comprises an electromagnetic valve.
`Preferably, the charging port means comprises a first port
`for use in refueling the fuel tank, and a second port for use
`on occasions other than refueling the fuel tank, the first port
`being connected via a first charging passage to the fuel tank,
`the second port being connected via a second charging
`passage to the fuel tank.
`More preferably, the evaporative fuel-adsorbing device
`include a control valve arranged in the first charging pas
`sage, and valve control means for opening the control valve
`when the fuel tank is refueled.
`To attain the second object, according to a second aspect
`of the invention, there is provided an evaporative emission
`control system for an internal combustion engine having a
`fuel tank and an intake passage, including an evaporative
`fuel-adsorbing device for adsorbing evaporative fuel gener
`ated from the fuel tank, a charging passage connecting
`between the evaporative fuel-adsorbing device and the fuel
`tank for introducing the evaporative fuel generated from the
`fuel tank into the evaporative fuel-adsorbing device, a
`purging passage connecting between the evaporative fuel
`adsorbing device and the intake passage for purging the
`evaporative fuel adsorbed by the evaporative fuel-adsorbing
`device into the intake passage, and an air-inlet passage
`connected to the evaporative fuel-adsorbing device and
`communicating with the atmosphere.
`The evaporative emission control system according to the
`second aspect of the invention is characterized in that the
`evaporative fuel-adsorbing device comprises:
`a first adsorbent chamber to which the charging passage
`and the purging passage are connected;
`a second adsorbent chamber to which the air-inlet passage
`is connected;
`absorbents charged, respectively, in the first adsorbent
`chamber and the second adsorbent chamber for adsorb
`ing the evaporative fuel;
`communication passage means connecting between the
`first adsorbent chamber and the second adsorbent
`chamber;
`flow rate-changing means for changing a maximum flow
`rate of the evaporative fuel through the communication
`passage means, in dependence on at least one of an
`amount of the evaporative fuel flowing into the evapo
`rative fuel-adsorbing device and an amount of the
`evaporative fuel flowing out of the evaporative fuel
`adsorbing device.
`Preferably, the charging passage comprises a first charg
`ing passage for introducing evaporative fuel generated when
`the fuel tank is refueled into the first adsorbent chamber, and
`a second charging passage for introducing evaporative fuel
`generated on occasions other than when the fuel tank is
`refueled.
`More preferably, the evaporative emission control system
`includes a control valve arranged in the first charging
`passage, and valve control means for opening the control
`valve when the fuel tank is refueled.
`Also preferably, the charging port means is connected to
`the fuel tank, and the communication passage means com
`prises a first passage which is constantly open, and a second
`passage, the flow ratechanging means opening the second
`communication passage at least when the fuel tank is
`refueled.
`
`4
`Further preferably, the flow rate-changing means com
`prises valve means arranged in the second passage, the valve
`means opening at least when the fuel tank is refueled.
`Also preferably, the flow rate-changing means comprises
`valve means arranged in the second passage, the valve
`means opening when the fuel tank is refueled and when the
`evaporative fuel is purged from the evaporative fuel-adsorb
`ing device.
`Still more preferably, the valve means arranged in the
`second passage comprises a one-way valve which opens
`when pressure within the first adsorbent chamber is higher
`than pressure within the second adsorbent chamber by a
`predetermined amount or more.
`Even more preferably, the valve means arranged in the
`second passage comprises a first one-way valve which opens
`when pressure within the first adsorbent chamber is higher
`than pressure within the second adsorbent chamber by a
`predetermined amount or more, and a second one-way valve
`which opens when the pressure within the second adsorbent
`chamberis higher than the pressure within the first adsorbent
`chamber by a predetermined amount or more.
`Also preferably, the valve arranged in the second passage
`comprises an electromagnetic valve.
`The above objects, features, and advantages of the inven
`tion will be more apparent from the following detailed
`description taken in conjunction with the accompanying
`drawings.
`
`BRIEF EDESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram showing the whole arrangement
`of an evaporative emission control system for an internal
`combustion engine, according to a first embodiment of the
`invention;
`FIG. 2 is a graph showing the relationship between a flow
`rate of evaporative fuel introduced-from a first activated
`carbon chamber to a second activated carbon chamber and
`the flow resistance of communication passages between the
`two chambers;
`FIG.3 is a block diagram showing the whole arrangement
`of an evaporative emission control system for an internal
`combustion engine, according to a second embodiment of
`the invention;
`FIG. 4 is a sectional view showing an evaporative fuel
`adsorbing device as part of an evaporative emission control
`system according to a third embodiment of the invention;
`FIG. 5 shows a variation of the evaporative fuel-adsorb
`ing device of the third embodiment shown in FIG. 4; and
`FIG. 6 shows another variation of the evaporative fuel
`adsorbing device of the third embodiment shown in FIG. 4.
`
`DETALED DESCRIPTION
`
`The invention will now be described in detail with refer
`ence to the drawings showing embodiments thereof.
`Referring first to FIG. 1, there is shown the whole
`arrangement of an evaporative emission control system for
`an internal combustion engine according to an embodiment
`of the invention.
`The evaporative emission control system 11 for control
`ling the emission of evaporative fuel into the atmosphere is
`comprised of a fuel tank 23 of an internal combustion engine
`1 equipped with a filler cap 22 which is opened or removed
`when the fuel tank 23 is refueled, a canister 26, as an
`evaporative fuel-adsorbing device, accommodating adsor
`bents 24, 24' formed of activated carbon, a first charging
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`passage 27 for ordinary use, connecting between the canister
`26 and the top of the fuel tank 23, a second charging passage
`33 for use in refueling, connecting between a portion of the
`fuel tank 23 in the vicinity of the filler cap 22 and the
`canister 26, an electromagnetic valve 34 for use in refueling
`arranged across the second charging passage 33 for selec
`tively opening and closing the same, a purging passage 10
`connecting between the canister 26 and an intake pipe 2 of
`the engine 1 at a location downstream of a throttle valve 3
`arranged in the intake pipe 2, and a purge control valve 36
`formed by an electromagnetic valve and arranged across the
`purging passage 10. The electromagnetic valve 34 and the
`purge control valve 36 are connected to an electronic control
`unit (ECU), not shown, to be controlled by driving signals
`therefrom.
`The canister 26 is divided by a partition 41 into a first
`activated carbon chamber 42 and a second activated carbon
`chamber 43. The first and second activated carbon chambers
`42, 43 are defined by a canister casing 26a, upper and lower
`retainer plates 46, 47, and the partition 41. The upper and
`lower retainer plates 46, 47 are formed of a porous material,
`and has inner side surfaces thereoflined with filters 48, 49,
`respectively. The first and second activated carbon chambers
`42, 43 are densely charged with activated carbon adsorbents
`24, 24' of almost the same kind in almost the same amount.
`The top of the first activated carbon chamber 42 is formed
`with an inlet port. 27a for ordinary use, which is connected
`to the first charging passage 27, an inlet port 33a for use in
`refueling, which is connected to the second charging passage
`33, and an outlet (discharge) port 10a which is connected to
`the purging passage 10. The inlet ports 27a and 33a extend
`through the upper retainer plate 46 and the filter 48 to
`directly open into the activated carbon adsorbent 24, while
`the output let port 10a opens into a gap between the casing
`26a and the upper retainer plate 46. Further, the second
`activated carbon chamber 43 has an air-inlet port 25a formed
`through the top thereof. The air-inlet port 25a has one end
`thereof opening into a gap between the casing 26a and the
`upper retainer plate 46, and the other end connected to an
`air-inlet passage 25 communicating with the atmosphere.
`Further, below the partition 41, a communication passage 52
`is formed in the canister 26, which is defined between the
`casing 26a and the lower retainer plate 47, through which
`the first activated carbon chamber 42 and the second acti
`vated carbon chamber 43 are communicated with each other.
`Further, a bypass passage 53 is formed in parallel with the
`communication passage 52 and connecting between the first
`activated carbon chamber 42 and the second activated
`carbon chamber 43 via the communication passage 53 to
`bypass the communication passage 52. The bypass passage
`53 has a one-way valve 55 arranged therein. The one-way
`valve 55 opens only when pressure within the first activated
`carbon chamber 42 is higher than that within the second
`activated carbon chamber 40 by a predetermined amount or
`more to thereby establish another communication path
`(bypass) between the first activated carbon chamber 42 and
`the second activated carbon chamber 43.
`Arranged in the intake pipe 2 at locations downstream of
`an end of the purging passage 10 opening into the intake
`pipe 2 are fuel injection valves 6 which are connected to the
`fuel tank 23 via a fuel supply pipe 7 and a fuel pump 8
`arranged in the fuel supply pipe 7. The fuel tank 23 has a
`tank internal pressure sensor 29 and a fuel amount sensor 30
`mounted in the top thereof for detecting pressure within the
`fuel tank 23 and for detecting an amount of fuel within the
`fuel tank 23, respectively. The fuel tank 23 also has a fuel
`temperature sensor 31 inserted through a side wall thereof
`
`6
`for detecting the temperature of fuel within the fuel tank 23.
`Next, description will be made as to how the evaporative
`emission control system constructed as above adsorbs
`evaporative fuel in the canister 26, and how it purges
`adsorbed fuel from the canister 26. First, when the vehicle
`is parking with the engine in stoppage or when the engine is
`in operation, evaporative fuel generated from the fuel tank
`23 is guided via the first charging passage 27 and the inlet
`port 27a into the first activated carbon chamber 42 of the
`canister 26. Most of the evaporative fuel is adsorbed by the
`activated carbon adsorbent 24 charged in the first activated
`carbon chamber 42, and a slight amount thereof is further
`guided via the communication passage 52 below the parti
`tion 41 into the second activated carbon chamber 43. The
`slight amount of evaporative fuel is adsorbed by the acti
`wated carbon adsorbent 24' within the second activated
`carbon chamber 43. At this time, the electromagnetic valve
`34 is not supplied with a driving signal from the ECU, not
`shown, and hence in a closed state, so that no evaporative
`fuel is guided via the charging passage 33 into the canister
`26.
`Next, description will be made as to evaporative fuel
`generated from the fuel tank 23 is guided when the fuel tank
`is refueled. In refueling, the electromagnetic valve 34 is
`opened by a driving signal from the ECU. At this time,
`evaporative fuel is vigorously generated, and guided into the
`first activated carbon chamber 42 of the canister 26 via the
`second charging passage 33 for use in refueling which
`extends into the fuel tank 23 at a location in the vicinity of
`the filler cap 22 and the inlet port 33a for use in refueling
`which extends into the canister 26. The evaporative fuel
`introduced into the first activated carbon chamber 42 flows
`therethrough while being adsorbed by the activated carbon
`adsorbent 24. At this time, the interior of the first activated
`carbon chamber 42 is pressurized by the evaporative fuel
`flowing therein to a level high enough to forcibly open the
`one-way valve 55 in the bypass passage 53 to thereby
`establish additional communication between the first acti
`wated carbon chamber 42 and the second activated carbon
`chamber 43 through the bypass passage 53. FIG.2 shows the
`relationship between the flow rate of evaporative fuel guided
`from the first activated carbon chamber 42 to the second
`activated carbon chamber 43 and the flow resistance of the
`communication passages 52, 53 between the two chambers.
`In the figure, Region. A designates a range of flow rate of
`evaporative fuel which can be assumed when the vehicle is
`parking, while Region B a range of same which can be
`assumed when the vehicle is refueled. When the one-way
`valve 55 is opened, the flow resistance of the communication
`passages 52, 53 between the first activated carbon chamber
`42 and the second activated carbon chamber 43 markedly
`decreases (the maximum flow rate of evaporative fuel via
`the communication passage 52 and the bypass passage 53
`increases), so that an overflow of evaporative fuel from the
`first activated carbon chamber 42 rushes into the second
`activated carbon chamber 43 to be fully adsorbed by the
`activated carbon adsorbent 24 in the second activated carbon
`chamber 43.
`Since the inlet port 27a for ordinary use and the inlet port
`33a for use in refueling extend through the upper retainer
`plate 46 into the first activated carbon chamber 42 charged
`with the activated carbon adsorbent 24, evaporative fuel
`guided into the first activated carbon chamber 42 via the fuel
`port 33a cannot reversely flow into the inlet port 27a,
`Next, how the adsorbed fuel is purged from the canister26
`will be described. In purging the adsorbed fuel, the ECU
`supplies a driving signal to the purge control valve 36
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`arranged across the purging passage 10 to open the same.
`Purging of the adsorbed fuel is carried out when the engine
`1 is in a predetermined operating condition, in which nega
`tive pressure or vacuum is developed within the intake pipe
`2. Vacuum in the intake pipe 2 is introduced into the first
`activated carbon chamber 42 via the purging passage 10 and
`the purge control valve 36 which is open, and further via the
`communication passage 52 into the second activated carbon
`chamber 43. Consequently, fresh air flows into the second
`activated carbon chamber 43 via the air-inlet passage 25 and
`the air-inlet port 25a. The flowing-in air causes the adsorbed
`fuel to be desorbed from the activated carbon adsorbent 24,
`and a mixture of the desorbed fuel and air flows from the
`second activated carbon chamber 43 into the second acti
`vated carbon chamber 42 via the communication passage 52.
`The adsorbed fuel is caused to be desorbed from the acti
`wated carbon adsorbent 24 in the first activated carbon
`chamber 42 as well, and the desorbed fuel is guided via the
`purging passage 10 into the intake pipe 2 to be drawn into
`combustion chambers of the engine 1.
`Thus, the evaporative fuel generated ordinarily and in
`refueling, is adsorbed by the activated carbon adsorbents 24
`and 24' in the first activated carbon chamber 42 and the
`second activated carbon chamber 43, which enhances the
`utilization factor of the activated carbon. Therefore, the
`amount of activated carbon can be curtailed as compared
`with the conventional arrangement in which separate can
`isters accommodating activated carbon adsorbents are pro
`vided, respectively, for use in refueling and for ordinary use.
`Further, since the single purging passage 10 is provided,
`which dispenses with provision of a plurality of purging
`passages, simplifying the construction of the evaporative
`emission control system.
`Although in the above described embodiment, the first
`activated carbon chamber 42 and the second activated
`carbon chamber 43 accommodate substantially the same
`kind of activated carbon as the adsorbents 24, 24' in sub
`stantially the same amount, this is not limitative, but it goes
`without saying that different kinds of activated carbons may
`be used. For example, the first activated carbon chamber
`may be designed larger in size or volume than the second
`activated carbon chamber so that the latter accommodates a
`larger amount of activated carbon than the latter. Further,
`activated carbons having different properties may be used
`depending on components of evaporative fuel to be adsorbed
`thereby. For example, the first activated carbon chamber 42
`may contain an activated carbon suitable for adsorbing
`components of evaporative fuel having relatively high boil
`ing points, while the second activated carbon chamber 43
`may contain an activated carbon suitable for adsorbing ones
`having relatively low boiling points. Further, although in the
`above described embodiment, the one-way valve 55 opens
`to decrease the flow resistance of the communication pas
`sageway between the first activated carbon 42 and the
`second activated carbon 43 when the vehicle is refueled, this
`is not limitative, but an electromagnetic valve may be
`employed instead of the one-way valve so that the opening
`and closing of the bypass passage is controlled by a control
`signal from the ECU.
`Next, a second embodiment of the invention will be
`described with reference to FIG. 3. In this embodiment, and
`a third embodiment, described hereinafter, component parts
`and elements appearing in FIG. 3, and FIG. 4 to FIG. 6,
`which correspond to ones of the first embodiment appearing
`in FIG. 1 are designated by identical reference numerals, and
`detailed description thereof is omitted.
`The second embodiment is distinguished from the first
`
`55
`
`60
`
`65
`
`8
`embodiment in that a two-way valve 60 is arranged across
`the first charging passage 27 for ordinary use and refueling
`detecting means 62 is provided in the vicinity of an upper
`end of a fuel tube 61, for detecting insertion of a filler gun
`or removal of a filler cap 22, and a signal indicative of
`detection by the refueling-detecting means 62 is supplied to
`the ECU.
`When the pressure within the fuel tank 23 becomes higher
`than atmospheric pressure by a predetermined amount (e.g.
`2.7 kilopascal) or more when the vehicle is parking with the
`engine in stoppage or when the engine is in operation, the
`two-way valve 60 opens to allow evaporative fuel generated
`from the fuel tank 23 to be guided via the first charging
`passage 27 and the inlet port 27a into the first activated
`carbon chamber 42 of the canister 26.
`The two-way valve 60 also opens when the pressure
`within the fuel tank 23 becomes lower than the pressure
`within the first activated carbon chamber 42 by a predeter
`mined amount or more, whereby evaporative fuel in the
`canister 26 is returned to the fuel tank 23.
`Next, the third embodiment of the invention will be
`described with reference to FIG. 4. Elements and parts of the
`arrangement of the evaporative emission control system
`omitted from FIG. 4 is identical to those of the arrangement
`shown in FIG. 1.
`In the present embodiment, in addition to the one-way
`valve (charging valve) 55, a one-way valve (purging valve)
`56 is arranged in the bypass passage 53 in parallel with the
`one way valve 55. The one-way valve 56 opens when the
`pressure within the second activated carbon chamber 43
`becomes higher than the pressure within the first activated
`carbon chamber 42 by a predetermined amount or more.
`According to this construction of the canister 26, the
`one-way valve 55 opens only when the fuel tank 23 is
`refueled, while the one-way valve 56 opens at the time of
`purging when the pressure within the second activated
`carbon chamber 43 becomes higher than the pressure within
`the first activated carbon chamber 42. This opening opera
`tion of the one-way valve 56 markedly decreases the flow
`resistance of the communication passageway between the
`first activated carbon chamber 42 and the second activated
`carbon chamber 43 (the maximum flow rate of gases through
`the total communication passage (the communication pas
`sage 52+ the bypass passage) increases) in purging as well,
`so that desorption of evaporative fuel from the activated
`carbon adsorbents 24, 24' is smoothly effected. As a result,
`it is possible to purge the adsorbed fuel within a short time
`period to enhance the utilization factor of the adsorbents
`(activated carbon) within the canister.
`FIG. 5 shows a variation of the arrangement of the two
`one-way valves 55 and 56. In this variation, the two valves
`55, 56 are disposed such that they open when their respec
`tive valve elements move in opposite directions to each
`other,
`Further, as shown in FIG. 6, a further variation may be
`adopted in which the two one-way valves 55 and 56 are
`replaced by an electromagnetic valve 57 which is controlled
`by the ECU 58 to open onl